The invention relates to a device for attenuating pressure surges of liquids, e.g. of a biologically vulnerable liquid, flowing inside a liquid conduit and for cleaning, in particular sterilizing, the liquid conduit comprising a bypass conduit that bridges over a section of the liquid conduit, wherein an isolating valve as well as a gas supply conduit are provided in the liquid conduit between the outlets of the bypass conduit.
For the transport of liquids through liquid conduits, in particular for the purpose of filling them into containers, the liquids must be brought to particular flow values by means of control and/or check valves in their flow, or the flow of the liquids must be interrupted, respectively, for instance, upon reaching a predetermined filling level in the container. Therefore, pressure variations that are more or less large constantly arise in the liquid conduits. Those variations can be very substantial and in large filling plants, for instance for the bottling of beer, milk, etc., they may exhibit a pulsating characteristic.
Pressure surges can amount to maximum pressures of more than two and a half times the normal liquid-conduit pressure. Thereby, excessive strain is put on the fittings and other appliances such as membrane filters, plate heat exchangers and especially also gaskets. In the case of higher static conduit pressures, such pressure surges must be rated as even more critical in terms of the hypothesis of fatigue strength.
For the purpose of providing a remedy, it is known to use air vessels for attenuating the pressure surges. Such air vessels are indeed a proven and simple attenuation means; however, different pressures in the liquid conduits require differently sized gas spaces in the air vessel which exhibit different characteristic frequencies, which may lead to problems for downstream electronic controls. A further great disadvantage of such air vessels is that cleaning is not possible during an operation cycle. Cleaning an air vessel requires that the same is shut off from the pipeline, whereby, after the cleaning process, the danger that remains of the detergent are present cannot be ruled out. Complete flushing of the air vessel is feasible only in a time-consuming way.
It has also been attempted to attenuate pressure surges with electronic methods, i.e. to provide electronic control and attenuation means. Those, however, depend on the velocity of the sensors and actuators of the system. Nevertheless, especially in high-frequency oscillations, resonances can occur which often aggravate the problem of pressure surges. On the other hand, excess attenuation of the system might also lead to pressure variations which are no longer compensable. In this connection, the occurrence of strongly varying frequencies of the pressure surges constitutes a particular problem.
From utility model document AT 001740 U1, a shunt pipeline, i.e. a bypass conduit, leading to a liquid conduit such as a beer conduit is known, which pipeline is filled with gas in the normal state and serves for the absorption of pressure surges. In that known device, pressure surges might, however, strike through the bypass conduit. Furthermore, it is cumbersome to carry out a purification, in particular involving a sterilization liquid, since, on the one hand, the bypass conduit and, on the other hand, the liquid conduit are to be treated separately, and furthermore a product change will result in difficulties as a result of an inadmissable mixture of the various products successively flowing through the liquid conduit.